The present invention relates to optical recording and reproducing apparatus which magneto-optically reads and writes data out of and to a magneto-optical recording medium, magneto-optical magnetic heads and magneto-optical magnetic recording mediums.
Conventionally, various system are proposed as a magneto-optical recording and reproducing apparatus, one example of which casts a circularly polarized light beam on a recording layer of a magneto-optical medium to generate a local magnetic field therein, switches the direction of the magnetic field depending on whether the rotational direction of the electrical vector of the polarized light beam is clockwise or counterclockwise to locally reverse the direction of magnetization of the recording layer of the medium to thereby record data on the recording layer, as disclosed in JP-A-2-181043 published Aug. 7, 1991.
In this conventional system, the means which switches the right- and left-handed rotation directions of the circularly polarized light beam uses an arrangement which rotates the positional relationship of a polarizer which constitute an optical system of the optical head and a 1/4 wave plate, relative to the optical axis and each other.
A laser light source used in a magneto-optical disk device and a magneto-optical tape device is disclosed, for example, in JP-A-3-11783 and 3-18835.
When information is recorded in conventional magneto-optical recording and reproducing apparatus such as magneto-optical disk devices and magneto-optical tape devices, a magnetic field having a predetermined direction is applied to a recording medium and simultaneously a light beam of a predetermined strength is cast on the medium to erase the information recorded already on the medium, then a magnetic field of an opposite direction and a light beam having a modulated strength is cast simultaneously on the medium to record information on the medium. Thus, it takes much time for the information to be recorded. In addition, a magnetic head which applies the magnetic field is required.